Epoxies are an important class of thermosetting polymers that are extremely robust. Their durability resulting in it being the material of choice for many long term applications such as adhesives, structural materials, paints, coatings, potting, printed circuit boards, microelectronic encapsulation, and other consumer goods. Epoxy resins are hardened or cured by a cross-linking reaction. The properties and applications of cured resin are greatly influenced by the choice of the hardener formulation and/or the method of curing. The cross-linking reactions are essentially irreversible. Therefore, the material cannot be melted and reshaped without decomposition of the material. Hence, the removal, recycling and reworkability of epoxies are notoriously difficult, which raises concerns about the longevity of epoxy-based materials in the environment.
Development of a “reworkable” epoxy material would have implications in recycling, recovery, and waste disposal. Furthermore, an easily removable epoxy could expand the use of epoxies into new consumer markets. For instance, joints could be bonded with epoxy glue and any spill-over could be easily removed, even post-curing, while the joint remains bonded. As another example, epoxy based paints and varnishes could also be more easily removed.
In some applications, epoxies are used in art conservation as adhesives for artifact reconstruction and repair. For example, epoxy thermoset adhesives are attractive for art conservation because of their strength and good adhesion. However, while originally brown in color, the development of colorless epoxies has made it has become more difficult to detect repair work and even if adhesives have been used on an artifact. Fluorescent epoxies would allow for easy detection of the epoxy joints by simple visual inspection under ultraviolet (UV) light UV light, while remaining unnoticeable under normal display lighting. Furthermore, only minute amounts of fluorescent dye are needed to make the epoxy adhesive fluoresce. However, the non-covalently attached dye can leach or be extracted from the adhesive bond, thereby attenuating or eliminating the fluorescent signature. Furthermore, adding even small amounts of a dye to the epoxy can change the mechanical properties of the resulting thermoset, often weakening it through plasticization. Hence, there is a need for an epoxy adhesive composition that allows for visible fluorescence in the thermoset without diminishing the strength of the adhesive.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.